The invention relates to apparatus for rapidly vibrating tubes containing samples, in particular biological samples, the rapid vibration of the tubes serving to grind up the samples.
It is already known to grind up biological samples by enclosing the samples in tubes that also contain microbeads made of glass or ceramic, and by subjecting the tubes that are closed in leaktight manner to axial vibration at high speed, e.g. at about 100 hertz (Hz), for a relatively short duration, of the order of 30 seconds (s) to 60 s, for example.
U.S. Pat. No. 5,567,050 describes apparatus for performing such a method and comprising a tube support disk and means for imparting oscillating motion to the disk about a center of rotation. The drive means comprise an electric motor whose outlet shaft is provided with a sleeve having an outside cylindrical surface that slopes obliquely relative to the axis of the outlet shaft of the motor. The sleeve is mounted free to rotate in the disk by means of rolling bearings in axial alignment, and the disk is associated with means for preventing it from rotating, so that when the sleeve is rotated by the motor, it causes the disk to oscillate about a center of rotation which is formed by the intersection between the axis of the motor shaft and the axis of the cylindrical outside surface of the sleeve. Tubes fixed at the periphery of the disk at equal distances from the center of rotation are thus subjected to substantially curvilinear reciprocating motion. In theory, the speed of rotation of the outlet shaft from the motor can lie in the range 3000 revolutions per minute (rpm) to 8000 rpm, and the samples are subjected to linear accelerations lying in the range 150 g to 400 g in order to be ground up, where g is the acceleration due to gravity.
Nevertheless, that known apparatus presents the drawback of the rolling bearings that serve to mount the disk on the sleeve and that support all of the forces for driving the disk, heat up rapidly, thereby causing the rolling bearings to wear quickly and very significantly reducing their lifetime, with the heating-up of the rolling bearings also leading to heating of the disk, which heat is then transmitted to the tubes and to the samples contained in the tubes. In practice, with that type of apparatus, it is not possible to cause the disk to oscillate at a speed greater than about 6000 rpm without destroying the apparatus fairly quickly. In addition, the heating of the rolling bearings and of the disk make it necessary to pause for a certain length of time between two grinding cycles, so as to allow the disk and the rolling bearings to cool down sufficiently.
Furthermore, in that prior art apparatus, the tubes need to be handled one by one in order to be placed in the housings provided in the disk, and in order to be taken away therefrom, and it is also necessary to install and maneuver by hands means for locking the tubes in their housings in the disk, thereby greatly lengthening the times required for loading and unloading the apparatus, thereby correspondingly increasing the total durations of sample analysis cycles.